A conventional refrigerant cycle device is configured to be capable of switching a cooling operation mode for a fluid to be heat exchanged and a heating operation mode for heating a fluid to be heat exchanged.
For example, a refrigerant cycle device described in JP-A-2005-306300 is used for a vehicle air conditioner. The refrigerant cycle device includes a utilization side heat exchanger for exchanging heat between a refrigerant and air to be blown into a vehicle compartment as the fluid to be heat exchanged, an outdoor heat exchanger for exchanging heat between the refrigerant and ambient air, and a four-way valve as a flow passage switch portion for switching a refrigerant flow passage. The four-way valve switches the refrigerant flow passage so that both the cooling operation mode and the heating operation mode can be achieved.
More specifically, in the cooling operation mode for cooling the air to be blown into the vehicle compartment, the refrigerant flow passage is switched such that the utilization side heat exchanger functions as an evaporator for evaporating the refrigerant and the outdoor heat exchanger functions as a radiator for radiating heat of the refrigerant. In the heating operation mode for heating the air to be blown into the vehicle compartment, the refrigerant flow passage is switched such that the utilization side heat exchanger functions as the radiator and the outdoor heat exchanger functions as the evaporator.
In order to improve coefficient of performance, that is, COP, of a cycle by increasing refrigeration capacity of the refrigerant cycle device, a so-called subcool condenser can be used for the heat exchanger that functions as the radiator.
As described in JP-A-2001-108331, for example, the subcool condenser is a heat exchanger that includes a condensation heat exchange portion for condensing the refrigerant, a receive portion for separating the refrigerant flowing out of the condensation heat exchange portion into gas and liquid phases, and a supercool heat exchange portion for supercooling saturated liquid phase refrigerant flowing out of the receive portion. Thereby, enthalpy of the refrigerant that flows into the evaporator is decreased and refrigerant capacity obtained by the evaporator can be increased.
Therefore, in the refrigerant cycle device of JP-A-2005-306300, when the subcool condenser is used as the outdoor heat exchanger functioning as the radiator in the cooling operation mode, for example, refrigeration capacity obtained by the utilization side heat exchanger functioning as the evaporator can be increased and COP can be improved.
However, in the refrigerant cycle device, the outdoor heat exchanger is functioned as the evaporator in the heating operation mode, in which the utilization side heat exchanger is functioned as the radiator. Thus, when the subcool condenser is used as the outdoor heat exchanger in the heat operation mode, COP may be deteriorated.
The reason will be described in detail with reference to FIG. 9 and FIG. 10. FIG. 9 is a schematic diagram showing a whole configuration of a general refrigerant cycle device that is configured to be capable of switching the cooling operation mode and the heating operation mode. Hereinafter, the general refrigerant cycle device is referred to as a test refrigerant cycle device. The respective reference numerals shown in FIG. 9 correspond to respective elements in embodiments described below.
FIG. 10 is Mollier diagram showing a state of a refrigerant of the test refrigerant cycle device. The cooling operation mode is shown by a solid line and the heating operation mode is shown by a dashed line and a dashed-dotted line.
In the test refrigerant cycle device, as shown by the solid line, a four-way valve 41 as the flow passage switch portion switches to a refrigerant flow passage, in which the refrigerant is circulated through a compressor 21, an outdoor heat exchanger 28, a pressure reducing device 44, a utilization side heat exchanger 42 and the compressor 21 in this order in the cooling operation mode. In contrast, as shown by the dashed line, the four-way valve 41 switches to a refrigerant flow passage, in which the refrigerant is circulated through the compressor 21, the utilization side heat exchanger 42, the pressure reducing device 44, the outdoor heat exchanger 28 and the compressor 21 in this order in the heating operation mode.
In the test refrigerant cycle device, the subcool condenser having a condensation heat exchange portion 283a, a receive portion 286 and a supercool heat exchange portion 283b is used as the outdoor heat exchanger 28.
Therefore, in the cooling operation mode, as shown by the solid line in FIG. 10, supercool degree of the refrigerant flowing out of the outdoor heat exchanger 28 can be increased (ΔE), and enthalpy difference between the enthalpy of the refrigerant at an inlet side and the enthalpy of the refrigerant at an outlet side in the utilization side heat exchanger 42, that is, refrigerant capacity in the utilization side heat exchanger 42, can be increased. As a result, COP in the cooling operation mode can be improved.
Because the subcool condenser functions to condense the refrigerant in the cooling operation mode, density of the refrigerant passing through the inside thereof increases gradually toward the outlet side from the inlet side of the subcool condenser. Thereby, a liquid phase refrigerant, the density of which is drastically increased compared to those of a gas phase refrigerant or a gas-liquid two-phase refrigerant, passes through the supercool heat exchange portion 283b. 
Therefore, in the subcool condenser, the refrigerant passage area is decreased gradually toward the outlet side from the inlet side, and the refrigerant passage area of the supercool heat exchange portion 283b is set to be the smallest. Thereby, an appropriate heat exchange area can be obtained and performance as the condenser itself can be obtained. Furthermore, miniaturization of the whole subcool condenser can be achieved.
However, in the heating operation mode, the subcool condenser is used as the evaporator for evaporating the refrigerant, and the refrigerant flows from the outlet side to the inlet side of the condenser in case where the subcool condenser is used as the radiator, that is, the condenser. That is, the flow direction of the refrigerant flowing through the subcool condenser in the heating operation mode is inverted with respect to the flow direction of the refrigerant flowing through the subcool condenser in the cooling operation mode.
Therefore, the gas-liquid two-phase refrigerant flows into the supercool heat exchange portion 283b, the refrigerant passage of which becomes the smallest in the subcool condenser, in the heating operation mode. Thereby, as shown by the dashed line in FIG. 10, pressure loss in the outdoor heat exchanger 28 may be drastically increased with respect to the utilization side heat exchanger 42 in the cooling operation mode.
Such the increase of pressure loss may increase driving force of the compressor, and COP in the heating operation mode may be deteriorated.
Even if the flow direction of the refrigerant flowing through the subcool condenser in the heating operation mode is the same with the flow direction of the refrigerant flowing through the subcool condenser in the cooling operation mode with respect to the test refrigerant cycle device, the deterioration of COP due to the above-described increase of pressure loss may be generated.
The reason is as follows. Because the evaporator functions to evaporate the refrigerant, the density of the refrigerant passing through the inside thereof decreases gradually toward the outlet side from the inlet side. In contrast, in the subcool condenser, as described above, because the refrigerant passage area is gradually decreased toward the outlet side from the inlet side, pressure loss may be increased toward the outlet side from the inlet side as shown by the dashed-dotted line in FIG. 10.